#43616C

CSS

:root {
  --under-the-sea: #43616c;
  --under-the-sea-rgb: 67 97 108;
  --under-the-sea-oklch: oklch(0.473 0.039 222.8);
}

.element {
  color: var(--under-the-sea);
  background-color: hsl(196 23% 34%);
  border-color: oklch(0.473 0.039 222.8);
}

Tailwind CSS v4

@theme {
  --color-under-the-sea: #43616c;
  --color-under-the-sea-50: #eaf8fe;
  --color-under-the-sea-100: #dbebf2;
  --color-under-the-sea-200: #c3d8e1;
  --color-under-the-sea-300: #a3bcc7;
  --color-under-the-sea-400: #86a4b0;
  --color-under-the-sea-500: #6a8c99;
  --color-under-the-sea-600: #5a7782;
  --color-under-the-sea-700: #485f68;
  --color-under-the-sea-800: #33464c;
  --color-under-the-sea-900: #233035;
  --color-under-the-sea-950: #121c20;
}

SCSS

$under-the-sea: #43616c;
$under-the-sea-rgb: 67, 97, 108;
$under-the-sea-light: mix(#fff, $under-the-sea, 20%);
$under-the-sea-dark: mix(#000, $under-the-sea, 20%);

.element {
  color: $under-the-sea;
  box-shadow: 0 0 0 2px rgba($under-the-sea, 0.35);
}